When it comes to gun deaths, medical examiners and public health scientists don’t agree on what “accidental” really means.

On March 31, a 17-year-old girl named Blake Turner died from a gunshot wound. Sheriff’s officials in Lenoir County, North Carolina, said she was accidentally shot by 22-year-old Austin Newcome. Newcome was charged with involuntary manslaughter and possession of a stolen firearm, and sheriff’s officials said the shooting was the direct result of handling that firearm “in an unsafe manner.” The local paper, too, called Turner’s death “accidental.”

But that’s not what the medical examiner called it.

“If the report says the gun was held by someone and it goes off, that, conventionally, most people agree, is called a homicide,” said Lorraine Lopez-Morell, a forensic pathology fellow at East Carolina University in Greenville, North Carolina. Lopez-Morell performed the autopsy on Turner and classified her death a homicide on the death certificate.

Turner’s death was colloquially an accident and technically a homicide, and that seemingly small difference has big implications. The public health officials who keep track of gun violence of all kinds tend to think of deaths like Turner’s the same way local reporters do — accidental (or, more accurately, unintentional). Medical examiners, the people who record the data that the public health researchers track, tend to classify these deaths as homicides. The result is that the public record of unintentional gun violence is riddled with inconsistencies, making it difficult to know how to approach the problem or, indeed, how large that problem even is.

Is this an accident?

According to the Centers for Disease Control and Prevention, which tracks all gun deaths in the U.S., there were 586 unintentional firearm deaths in 2014, down from 824 in 1999. People ages 20 to 24 had the highest rate of unintentional firearm deaths and made up 16 percent of the total. But we cannot take for granted that this count is accurate, experts told me. “What’s in there is garbage,” said Catherine Barber, research manager at the Harvard Injury Control Research Center. For instance, studies have found that discrepancies in the data and reporting are causing local governments to undercount the number of young children being killed in unintentional shootings, with the implication that such shootings might be undercounted across the board.

Accurate counts are crucial for those trying to figure out which policies might reduce the number of unintentional gun deaths. Inconsistent data is especially problematic for something like unintentional gun deaths, whose numbers are small to begin with, said Robert Anderson, chief of the CDC’s National Center for Health Statistics’ mortality statistics branch. His team manages the process of compiling vitals data from states for the National Vital Statistics System and making it available to the public. Those 586 unintentional firearm deaths in 2014 were counted through this system.1

Is this an accident?

If Anderson’s team were off by 50 cases in its count of intentional gun homicides, that wouldn’t make much of a difference to policymaking because there are more than 10,000 of those deaths annually. But with unintentional gun deaths, 50 cases could change the direction of national trends. It could mean the difference between a harm-reduction policy — for example, safe storage laws that make it mandatory for all guns in a home to be kept in a locked cabinet — appearing to be successful or appearing to be an abject failure.

“Anything where you say ‘we want to understand whether this has an impact on accidental gun deaths,’ you can’t use vitals data for that,” Barber said.

But accurately portraying the problem is probably not as simple as assuming that the number of unintentional firearms deaths is always higher than vitals data says it is. Research has found the data can include both false negatives — unintentional gun deaths that were recorded and tallied as homicides — and false positives — gun deaths that should not have been tallied as “unintentional” but were.

Is this an accident?

In 2011, Barber published a paper comparing 404 gun deaths in 16 states that were coded unintentional by the National Vital Statistics System to those she and her colleagues tallied using primary sources, including investigation case reports. When they did, they found that 42 percent of those 404 deaths weren’t actually unintentional. Descriptions of the events in death records and police reports made it clear they were homicides and suicides instead.

Some of the false positives are coding errors. Others happen because any non-natural death that has no manner listed on the death certificate is categorized as an accident.2 That rule makes sense for, say, a drowning. But gun deaths are seldom unintentional, Barber and medical examiners told me.

Barber and her team counted 381 unintentional gun deaths in those 16 states using their own methodology. Thirty-eight percent of those deaths were coded in the NVSS data as something other than “unintentional,” usually homicide.

Anderson said his team was aware that medical examiners often code any gun death where the gun was fired by another person as a homicide, but he wasn’t sure how big a difference that made in the final statistics. The center hasn’t yet done an internal evaluation and doesn’t know the scale of this or any other coding problems related to unintentional gun deaths.

Unintentional Gun Deaths Are Down

In 1981, the National Vital Statistics System recorded 1,871 unintentional firearm deaths nationwide. Over the next three decades, that number would steadily decline — down to 1,441 in 1991, 802 in 2001 and 591 in 2011. The annual tally leveled off around the high 500s in 2008, but the reduction that preceded it is impressive, mysterious, and almost never discussed, even among gun policy experts.

Allison Anderman — staff attorney for the Law Center to Prevent Gun Violence, a group that advocates for gun violence prevention — had never heard of this decrease. When I spoke to Robert Anderson, chief of the mortality statistics branch of the CDC’s National Center for Health Statistics, he had forgotten how big it was.

Despite the well-documented inconsistencies in the data on unintentional gun deaths, the researchers I spoke to believed that the decline was real. The specific numbers may not be correct, said Jon Vernick, co-director of the Center for Gun Policy and Research at Johns Hopkins. But “it’s a little hard for me to believe that the decline over the last 30 years is an artifact of how the data are coded,” he said. Even Harvard’s Catherine Barber, a critic of the data on unintentional gun deaths, thinks these deaths really have fallen — we just don’t know by exactly how much.

The apparent reduction in unintentional firearm deaths goes all the way back to 1950. And in the past 30 years, we’ve seen drops in other kinds of unintentional deaths: Unintentional drownings and unintentional fire deaths both fell between 1981 and 2014, and the rate of unintentional motor-vehicle deaths fell by half during those 30 years. This is why Barber thinks the apparent unintentional gun death decline is real — it’s in keeping with larger trends that aren’t affected by the inconsistencies that plague the gun death data.

But the causes of the drop in unintentional gun deaths have hardly been studied, so scientists can do little more than speculate about why it happened and why it stopped. For instance, Barber said that improved emergency room care might have something to do with the decline — maybe just as many people are getting accidentally shot as in 1981, but fewer of them are dying. But this doesn’t totally line up. For instance, from 1993 to 1998, one study found that as unintentional gun deaths fell from 1,521 a year to 866, the numbers of unintentional gun injuries fell, too. Since 2001, the injury numbers have showed no clear trend, falling for a couple of years before bouncing back up and then falling again.

Barber, Vernick and Anderson all mentioned reduced exposure to guns as another possible explanation for the change. The share of households that own guns fell from 47.3 percent in 1980 to 31.0 percent in 2014. And it may be, they suggested, that fewer Americans are hunting. But it’s hard to say how much less popular hunting has become. The federal General Social Survey asks respondents whether they, their spouse or both are hunters. In 2014, 15.4 percent said “yes,” compared with 28.3 percent in 1980. But the U.S. Census Bureau, which only has data going back to 1991, found 14.1 million hunters that year and 13.7 million in 2011, the most recent year it asked the question — not much of a dip.

Figuring out what caused the reduction in accidental gun deaths will take both research and better record-keeping, Vernick said. He compared the situation to the decline in motor-vehicle deaths, which happened because of a variety of policies, including seat belt laws, crackdowns on drunken driving and mandates for crash-test-approved child seats. We know what happened there, he said, partly because there was funding to study it and partly because we set up comprehensive data collection about all motor-vehicle deaths.

The Fatality Analysis Reporting System has been around since 1975, and, Vernick said, “any time there is a death on a public roadway, we descend on that death and collect information.” In contrast, the analogous system for gun deaths — the National Violent Death Reporting System — became operational in 2003 and still does not collect data from all 50 states.

At first I thought the medical examiners were miscategorizing deaths. If we could just get them to distinguish intent more clearly, we could eliminate the discrepancies. But this turns out to be extraordinarily difficult, if not impossible. Intention — and death itself — is not an easy thing to categorize.

The National Association of Medical Examiners issues guidelines for medical examiners and coroners to use as they decide which of five categories — natural, accident, suicide, homicide or undetermined — to choose for a given case’s manner of death. By those guidelines, there are very few situations that count as an unintentional shooting — for instance, guns that are dropped and discharge by themselves or guns that have a hair trigger and fire at the brush of a finger. The best way to think about it: An unintentional gun death is when guns kill people. A homicide is when people — even toddlers — kill people, regardless of intent.

But “guidelines” is the operative word. These are not rules. Different medical examiners will have different opinions, as will coroners.3

Most of the time, these differences of perspective won’t really matter, Randy Hanzlick told me. He’s the chief medical examiner for Fulton County, Georgia, and a former president of the National Association of Medical Examiners. The vast majority of deaths are straightforward and easy to call, he said. But in situations in which a medical examiner has to determine intent, things become messy very quickly. And the accident/homicide question is all about intent.

For instance, in a 2015 survey, medical examiners were asked to judge the manner of death for a scenario in which a 6-year-old fatally shot his 4-year-old brother after finding a loaded gun in their father’s drawer. Fifty-three percent of the respondents judged the manner of death to be homicide — pretty much everyone else called it an accident. But how do you know what a 6-year-old meant to do?

As far as the National Association of Medical Examiners is concerned, either option is a fine outcome. There are no right or wrong answers, Hanzlick said. If a medical examiner is sure the child didn’t intend to kill his brother, she could classify it as an accident. But, Hanzlick said, it’s easier to determine whether the child intended to pull the trigger — and, if so, just call it a homicide. “Homicide,” as a category, saves medical examiners from having to double as philosopher psychotherapists.

But the problem remains: People are trying to set policy and test its effectiveness based on incorrect data. The good news is that this is likely to change, thanks to the National Violent Death Reporting System.

This system, which like the National Vital Statistics System is a project of the CDC, draws on state vital statistics registries but adds information taken directly from medical examiner reports, as well as law enforcement case reports and other government documents. All that information goes to state abstractors — actual people who read the material, code it, write up narratives about what happened, and assign a manner of death category that takes into account all the available information. In her 2011 paper, Barber found that this abstractor system was much more accurate than the NVSS.

The usefulness of the National Violent Death Reporting System is currently limited: It has only collected data since 2003, and today it covers 32 states. In the future, the system will be able to give us clean data on unintentional gun deaths. But for now, we’re left without a way to analyze unintentional gun deaths over long periods of time, offer an accurate national count of these deaths, or make comparisons among states that aren’t part of NVDRS.

The National Center for Health Statistics is hoping to get a handle on how big the categorization problem is later this year. Anderson recently hired a staff member whose job will entail going back to death certificates and comparing what medical examiners wrote about a case — their description of the event, not just the manner of death — with the way that death was coded in NVSS. This won’t catch all the false negatives and false positives, he told me, but it should give his team an idea of how big the problem is. Then they’ll decide what to do next.

To people like Anderson, who think about types of gun deaths as individual categories with potential public health solutions, getting that data right is important. But, here again, medical examiners have a different perspective. Hanzlick and other medical examiners I spoke with were more focused on the big picture of gun violence and its relationship to crime. To them, a discrepancy in a small subcategory like accidental gun deaths just doesn’t matter that much.

Those deaths are tragic, Hanzlick said, but whether there are 586 annually, or 400, or 700, they still pale in comparison to the 11,409 intentional gun homicides that happened in 2014. “I’m not sure it’s worth all the worry,” he said.

Footnotes

This is the same database that we use in other stories in this series, where it’s called the Multiple Cause of Death database.

The exception to this is stabbing. Anderson said stabbings with no manner of death default to homicide. Gun deaths that have no manner of death recorded but are described in medical examiners’ notes as “self-inflicted” default to “undetermined.”

Medical examiners are always doctors, although they don’t all have the same training before taking on the medical examiner position. Coroners are elected and do not have to be doctors at all.

Maggie Koerth is a senior science writer for FiveThirtyEight. @maggiekb1